How Many Units Are in a Drink?

How the numbers work

The grams of pure alcohol in a drink come from a simple relationship: volume × ABV × the density of alcohol (0.789 g/mL). ABV — alcohol by volume — is the percentage on the label. A stronger drink or a bigger glass both push the alcohol content up, which is why a large glass of wine can carry far more than a single beer.

Because countries set the reference amount differently, the same beer counts as a different number depending on where you are. The US uses a 14 g standard drink; the UK uses an 8 g unit; other European countries commonly use 10 g. Our calculator lets you pick your region so the count matches your local guidelines.

Worked examples

A 12 fl oz (355 mL) beer at 5% ABV contains 355 × 0.05 × 0.789 ≈ 14 g of alcohol — one US standard drink, or about 1.8 UK units. A 5 fl oz (150 mL) glass of 12% wine holds 150 × 0.12 × 0.789 ≈ 14 g — also one standard drink. A 1.5 fl oz (44 mL) shot of 40% spirits gives 44 × 0.40 × 0.789 ≈ 14 g as well.

The catch is real-world servings. A craft beer at 8% or a generously poured 9 fl oz (250 mL) glass of wine can each be closer to two standard drinks, so an evening adds up faster than the glass count suggests. Checking the ABV on the label and the actual pour is the key to an honest tally.

Using units to drink less

Health authorities frame low-risk drinking in these units. Guidance varies, but a common message is to keep intake modest, spread it across the week and have several alcohol-free days. There is no level of alcohol that is completely risk-free, and less is better for long-term health.

Beyond the direct health risks, alcohol adds calories — about 7 kcal per gram — which can quietly undercut weight goals. Alternating alcoholic drinks with water, choosing lower-ABV options and measuring pours at home all help keep your count honest and your intake down.

Frequently asked questions

What is a US standard drink?

It is any drink containing 14 grams of pure alcohol — for example a 12 fl oz beer at 5%, a 5 fl oz glass of 12% wine, or a 1.5 fl oz shot of 40% spirits.

How does a US standard drink compare to a UK unit?

A UK unit is 8 grams of alcohol, while a US standard drink is 14 grams. So one US standard drink is roughly 1.75 UK units — the labels differ, the alcohol is the same.

Does drinking water dilute the alcohol I've had?

No. Water can reduce dehydration and pace your drinking, but it does not speed how fast your body clears alcohol, which happens at a roughly fixed rate over time.

Is there a safe amount of alcohol?

No level is completely risk-free. Health bodies advise keeping within low-risk guidelines and note that drinking less always lowers risk. If you are pregnant, on medication or have a health condition, ask a professional.